The present invention relates to a cutting tool for use especially in mining and road-working environments, which include a nozzle for spraying water onto a cutter bit.
Drum-type cutters are conventional in the mining and road-working industries for example, wherein cutter bits are mounted on a drum which rotates about a horizontal axis. Such cutters can be used to cut through minerals in a mine, or to rip up asphalt or concrete from a roadway, among other uses. The cutter bits, which are carried by holder blocks welded to the outer surface of the drum, are rotatable about their own longitudinal axes so as to be self-sharpening. During a cutting operation, not only do the bits tend to wear, but the holder blocks wear as well. That is, the area of the holder block that surrounds the bit-receiving bore wears due to abrasion thereof by the materials being cut. It will be appreciated that the need to replace the welded-on holder blocks results in a serious expenditure of time and money.
To minimize that problem, it has been proposed to mount each cutter bit in a replaceable hollow sleeve which is inserted into a respective holder block. The sleeve includes a wide flange that overlies the area of the holder block that surrounds the mouth of the bit-receiving bore, and thereby shields the holder block from appreciable wear. Instead, the sleeves become worn and are replaced when necessary.
It is also conventional to provide the drum or the blocks with nozzles that spray water in the direction of the cutter bits for cooling and flushing purposes. The cooling feature is especially beneficial in mining environments where explosive gases, such as methane, may be present. The presence of such gases presents the risk of explosions in response to so-called “friction ignition” wherein friction imposed against steel parts of the cutter bits produces beads of molten steel, the heat of which ignites the gases. By spraying cooling water against the cutter bit, the potential for such friction ignition is greatly reduced. The cooling water also extinguishes ignitions (normally occurring at the bit tip), and controls dust.
Examples of providing spray nozzles in the block can be found in U.S. Pat. Nos. 4,333,687; 6,099,081; 6,485,104; and British Patent 2092205.
It will be appreciated from U.S. Pat. No. 4,333,687 that the provision of a nozzle immediately next to the cutter bit requires that the diameter of the flange portion of the replaceable sleeve be greatly reduced, thereby diminishing the amount of wear protection afforded thereby.
The provision of spray nozzles in an extension of the block, as in U.S. Pat. Nos. 6,099,081; and 6,485,104 serves to increase the amount of wearable surface area of the block and also displaces the nozzles farther from the cutter bit.
The provision of a nozzle in a separate bushing that surrounds the sleeve, as disclosed in British Patent 2092205, adds further cost and complexity to the system and places the nozzle somewhat laterally remote from the cutter bit.
It would be desirable to provide a nozzle for such a cutter bit which is positioned close to the cutter bit without adversely affecting the wear protection afforded by the replaceable flange.
In U.S. Pat. No. 4,678,238 there is disclosed a rotary mining bit rotatably mounted in a sleeve that is secured in a holder block. The sleeve is in the form of a two-step sleeve that is received in a two-step bore of the holder block, wherein the sleeve is fully recessed in the holder block. A coolant passage is formed in the holder block and communicates with an annular passage formed between the bore and the sleeve. The annular passage communicates with a water spray passage extending through a large-diameter portion of the sleeve. A roll pin extends through the aligned holes of the holder block and the sleeve to prevent rotation of the sleeve. The water spray passage is oriented to spray water toward a tip of the bit. However, because of the need to position the roll pin in aligned holes of the holder block and the sleeve, the sleeve (and thus the water spray passage) can be placed in only one orientation relative to the holder block, which might not be optimal for the particular location of the holder block on the mobile carrier (e.g., rotary drum). Also, because the sleeve is fully recessed within the bore, it offers no protection for the holder block against adhesive wear by cuttings.
It would be desirable to provide such a nozzle in a sleeve which protects the mounting block from abrasive wear by cuttings.
It would be further desirable to ensure that the nozzle can always be oriented in an optimal spray location, regardless of the particular location of the mounting block on the carrier.